[6.12] Getting Physical: Rotation Rate Determination for PHAs

The NASA Near Earth Object (NEO) search efforts have now
discovered more than 2300 objects, 500 of which are
classified as Potentially Hazardous Asteroids (PHAs). The
McDonald Observatory NEO team continues to participate in
the astrometric work of NEO confirmations and follow-up
observations. While finding and maintaining precise orbits
of these objects is essential in assessing the hazards they
might pose to Earth, the physical characteristics such as
mass, rotation rate and surface properties are important
factors in understanding their full dynamical evolution. The
efficiency of the proposed process for transporting objects
from the Main Asteroid Belt to Earth crossing orbits (i.e.,
resonances assisted by the YORP effect) depends on the above
properties. At the present we lack sufficient information on
the physical characteristics of most NEOs.

As a first step, we are attempting to obtain refined
absolute magnitudes, rotational periods, and, whenever
possible, axis ratios and three-color information for PHAs.
Relative photometry has been already carried out for 2002
EZ11 in the Johnson R band, and more are scheduled. The
results of these studies will be presented at the meeting.

This research is funded by NASA's NEO Observation Program
grants NAG5-6863 and NAG5-10183.